1. Field of the Invention
The present invention relates to a multicolor display apparatus (hereinafter, simply referred to as “display apparatus”) including a plurality of organic light-emitting devices (organic electroluminescent devices (hereinafter, sometimes simply referred to as “device”)) each having a pair of electrodes including an anode and a cathode, and a plurality of organic compound layers interposed between the pair of electrodes and including a light-emitting layer.
2. Description of the Related Art
At present, display apparatuses have been vigorously researched and developed. In an organic light-emitting device which constitutes a display apparatus, emitted light is reflected due to various refractive index differences, so that optical interference occurs. The optical interference length in the device will change depending on an angle at which the device is viewed, and the emission spectrum shifts toward shorter wavelengths side. That is, depending on the viewing angle, a red-light-emitting device shows an orange color, a green-light-emitting device shows a blue color, and a blue-light-emitting device shows a deeper blue color. Therefore, when a display apparatus is viewed from an oblique direction, the tints of the respective devices change, with the result that the white balance is lost.
In view of the foregoing, Japanese Patent Application Laid-Open No. H11-329742 (see p. 3, 11. 20 to 35; and FIG. 1) discloses a display apparatus in which the light-extraction side of a device is provided with a light diffusion color filter.
In addition, Japanese Patent Application Laid-Open No. 2002-367770 (see p. 3, 11. 17 to 25; and FIG. 1) discloses a display apparatus having a device provided with an optical resonator structure in which the peak wavelength of emission spectrum and the peak wavelength of multiple interference spectrum due to a resonating portion (wavelength at which light is most intensified by resonance) are offset with respect to each other. In an embodiment of the display apparatus, with respect to the peak wavelength of the emission spectrum, the peak wavelength of the multiple interference spectrum is set to be offset by +10 nm for red color, +4 nm for green color, and −10 nm for blue color. As a result, with the display apparatus, the white color shift at a viewing angle of 60° is suppressed.
Incidentally, a resonator structure is to resonate emitted light in a space (resonating portion) between a reflecting portion and a light-extraction portion located at an upper and a lower portions of a device. Accordingly, it can be said that all devices are each provided with a resonator structure, though differing from each other in the extent of a resonance effect.
With the technique disclosed in Japanese Patent Application Laid-Open No. H11-329742, emitted light is diffused when passing through the color filter, so that the change in tint depending on the viewing angle can be alleviated. However, the technique requires a step of forming the color filter. Accordingly, there is posed the problem such that the constitution of the display apparatus becomes complicated, which reduces the productivity and increases the production cost. In addition, there is also posed the problem that when the color filter is used, only a part of light emitted from a light-emitting layer can be extracted to the outside, which results in a reduction of the light extraction efficiency.
A device provided with a resonator structure is of such a constitution that light corresponding to a resonant wavelength is intensified and extracted to the outside of the device. Accordingly, in order that a narrow spectrum having a high peak intensity may be obtained, the peak wavelength of emission spectrum and the peak wavelength of multiple interference spectrum due to a resonating portion (wavelength at which light is most intensified by resonance) are preferably caused to coincide with each other. In this case, a device having a high efficiency and showing an excellent color purity can be realized. The technique disclosed in Japanese Patent Application Laid-Open No. 2002-367770 described above can suppress a white color shift depending on a viewing angle, but involves a problem in a trade-off relationship with the suppression effect, that the emission efficiency lowers as compared to that in the case where the peak wavelengths are caused to coincide with each other. In particular, when the emission efficiency of a device which shows an emission color with a relatively low luminous efficiency lowers, a larger amount of energy must be input in order that desired luminance may be obtained, so that a problem such as an increase in power consumption of the display apparatus occurs.